A well intersecting a subterranean hydrocarbon bearing reservoir that has been producing for an extended period of time and whose flow rate has decreased or stopped altogether may require a workover. Workovers may include any of several operations on the well to restore or increase production once a reservoir stops producing at the desired rate. Many workover jobs involve treating the reservoir, while other workover jobs involve repairing or replacing downhole equipment. In order to keep a well under control while it is being worked over, a workover fluid in commonly circulated downhole. The workover fluid is typically a water-based or oil-based mud that includes a variety of additives to establish certain desirable properties such as high viscosity and the ability to form a wall cake to prevent fluid loss. Most importantly, the workover fluid must be of a sufficient weight to overcome formation pressure.
In certain well installations, prior to circulating workover fluid into the well, communication must be established between the interior of a tubular string, such as a casing, a liner, a tubing or the like and the annulus surrounding the tubular string. One method for establishing such communication is through the use of explosives, such as shaped charges, to create one or more openings through the tubular string. The shaped charges typically include a housing, a quantity of high explosive and a liner. In operation, the openings are made by detonating the high explosive which causes the liner to form a jet of particles and high pressure gas that is ejected from the shaped charge at very high velocity. The jet is able to penetrate the tubular string, thereby forming an opening.
As hydrocarbon producing wells are located throughout the world, it has been found that certain jurisdictions discourage or even disallow the use of such explosives. In these jurisdictions and in other locations where or when it is not desirable to use explosives, mechanical perforators have been used to establish communication between the interior of a tubular string and the surrounding annulus. Such mechanical perforators may, for example, include a radially extendable punch that penetrates through the tubular string. In operation, the mechanical perforator is typically coupled to wireline activated jarring tool and run downhole on a wireline or similar conveyance. Once the mechanical perforator is positioned at the target location in the well, the jarring tool is energized via wireline manipulation and the energy stored in the jarring tool is then exerted on the mechanical perforator causing the punch to shift radially outwardly.
It has been found, however, that the use of a wireline activated jarring tool to actuate a mechanical perforator may be unreliable. For example, such operations have failed to produce the desired openings in the tubular string and have instead only resulted in deformation of the tubular string. Accordingly, a need has arisen for a more reliable tool system for establishing communication between the interior of a tubular string the surrounding annulus without using explosives.